Insertion Pipes given the choice between putting a item in the pipe in to an inventory (A chest or a furnace) and passing it along to another pipe, the Insertion Pipe will always try to add the item to the inventory.

This pipe is very useful for feedback loops as it forces the item to go in to the last machine if it can.

Extraction Pipe is the opposite of the Insertion Pipe. If the pipe can choose between an inventory and another pipe the pipe will always go with the next pipe. Also this pipe behaves the same as a wood pipe where it will pull items out of an inventory if the pipe has an active redstone engine applied to it.

This pipe is useful for tight spaces where you do not want a pipe to accidentally fill a chest or machine.